IwGame Engine v0.34 Released – Modifiers, Box2D Joints and Marmalade 6.0 fix

New here? What’s IwGame? IwGame is an open source free to use cross platform game engine for iPhone, iPad, Android, Bada, Playbook, Symbian, Windows Mobile, LG-TV, Windows and Mac, built on top of the Marmalade SDK. You can find out more and download the SDK from our IwGame Engine page.

Well this release is a little earlier I’m afraid, we wanted to get UI functionality into 0.34, but 0.33 had a compile issue with the recent Marmalade 6.0 release so we decided to do a release now.

Below is the list of changes for IwGame 0.34:

  • Fixed Marmalade 6.0 compile error
  • JPEG loading support has been removed as this is now supported by Marmalade image classes
  • New extensions system added (pass true for enable_extensions in IwGame::Init() to enable, enabled by default) – Extensions are none standard IwGame code that will be added over the coming months to support game specific features
  • Actions now have a 4th parameter
  • New modifier system added that allows you to add functionality units to actors and scene. This enables a build from blocks style development
  • New AddModifier action that can be used to add a modifier to an actor or scene and modifier its behaviour in real-time
  • New ChangeModifier action that can be used to change the active state or remove a modifier from an actor or scene
  • Actors can now be marked as draggable. A draggable actor can be moved aruond by the user using their finger
  • New SetProperty action added for actors. You can now directly change the properties of an actor using actions. Can also be used to add torque and force onto actors under control of the physics system
  • New AddProperty action added for actors. This action can be used to add a value onto the peoperties of an actor
  • IwGame now supports brushes in code and in XOML. Brushes can be created and attached to actors saving you from having to specify image and SrcRect for each actor. This enables actor styling across any actors
  • CIwGameActorImage can now be instantiated from XOML using the ActorImage tag
  • New XOML atlas inner tag added to animations to allow auto generation of sprite atlas frames
  • Support has been added for joints (distance, revolute, prismatic, pulley and wheel joints are supported in code and in XOML)
  • A scenes physics update can now be changed between constant time step and variable
  • Box2D materials now support bullet, fixed rotation and gravity scaling parameters
  • Checks for duplicates added to resources, variables, actions, modifiers, class creators
  • New CIwGameActorConnector extension actor added – This actor will size and orientate itself so that it connects two static / dynamic points in space (can target moving actors)
  • New CIwGameModFollowHeading modifier extension added – When added to an existing actor the actor can be controlled using headnig and speed instead of velocity
  • CIwGameImage::CreatePNG() now supports RGBA_8888
  • Two basic Hello World examples added, one that displays text in code and another that uses XOML
  • BUG FIX: IwGameBox2d now coompiles on Mac without error
  • BUG FIX: CIwGameBox2dBody::setFixture() now behaves as expected
  • BUG FIX: Collision flags are now restored when turning an object from none collidable to collidable
  • BUG FIX: Memory leak in CIwGameActorImage::SetSrcDest(), SetSrcRect() and SetDestSize()
  • BUG FIX: Fixed problem with html parsing in CIwGameAds::ExtractLinkAndImageFromtHTML()
  • BUG FIX: CIwGameImage::CreatePNG() crash bug fixed

Lots of changes and a few bug fixes for good measure. The most interesting changes include Box2D physics joints (been playing with them all week and they are awesome), the new modifiers system, draggable actors and the ability to set actor properties directly using actions. Lets look at some of these new changes in more detail:

Box2D Joints Support

Physics joints enable you to connect physical bodies together in a variety of ways. The following types of physical joints are currently supported:

  • Distance – A distance joint limits the distance of two bodies and attempts to keep them the same distance apart, damping can also be applied
  • Revolute – A revolute joint forces two bodies to share a common anchor point. It has a single degree of freedom and the angle between the two bodies can be limited. In addition a motor can also be applied to the joint
  • Prismatic – A prismatic joint limits movement between the two bodies by translation (rotation is prevented). The translational distance between the two joints can be limited. In addition a motor can also be applied to the joint
  • Pulley Joint – A pulley joint can be used to create a pulley system between two bodies so that when one body rises the other will fall.
  • Wheel Joint – A wheel joint restricts one body to the line on another body and can be used to create suspension springs. A motor can also be applied to the joint

All joints share the same base class IIwGameBox2dJoint

Joints can be created in code and attached to a body using CiwGameBox2dBody::addJoint(). Joints can later be removed using removeJoint(). You can also search for existing joints using getJoint() and findJoint()

        <ActorImage Name="Crate1" ...... />
        <ActorImage Name="Crate2" ...... >
                <Joint type="distance" ActorB="Crate1" OffsetA="0, 50" OffsetB="0, -50" Frequency="10" Damping="0" SelfCollide="true" />

The easiest way to create and attach joints is using XOML. Below is an example showing how to create and attach a distance joint between two crates:

Actor and Scene Modifiers

IwGame supports modifiers using the IwGameModfier system. Modifiers can be thought of as small functional building blocks that can be stacked in an actor or scene to extend the functionality of that actor or scene. For example, a typical modifier for a scene could be one that tracks the players scores / hi-scores, change day / night settings or detects special gestures. An actor modifier example could be a modifier that allows the actor move around using heading and speed or even a modifier with functionality specific to your game such as make a baddy that walks left and right on a platform. The idea is to allow developers to build games and apps up from smaller re-usable building blocks and be able to add them using code or XOML. Below is a quick example showing how to attach a modifiers list to an actor in XOML:

     <ActorImage Name="Baddy1" ....... >
              <Modifier Name="AddThrustMod" Active="true" Param1="1" />
              <Modifier Name="ShootPlayerWhenClose" Active="true" Param1="1" />

Here we have added two modifiers to the Baddy1 actor which modify its behaviour. Note that up to 4 parameters can be passed to the modifier

Modifiers can also be attached in code like this:

    // Find the modifiers creator
    IIwGameModifierCreator* creator = IW_GAME_MODS->findCreator("addthrustmod");
    if (creator != NULL)
        // Create an instance of the modifier
        IIwGameModifier* mod = creator->CreateInstance();
        if (mod != NULL)
            // Set up the instance
            mod->setParameter(0, "1");

            // Add the modifier to the actor

Draggable Actors

Any actor can now be set as draggable, allowing the user to tap it and drag it around the world. You can make any actor draggble in XOML by adding Draggable=”true” to its definition.

Setting / Updating Actor Properties from XOML

Its now possible to set or update actor properties directly from an action in XOML. Using the new SetProperty / AddProperty actions

Extensions System

From v0.34 of IwGame a new optional extensions system has been added. The extensions system is basically a collection of actors, scenes, actions, modifiers and other elements that are not part of the base IwGame engine. The extensions system provides support for game specific objects and other functionality that can be used to make creating specific types of games much easier. There’s not many extensions available yet but many more will be added in the future

IwGame Usage Changes

Please note the recent changes that have been applied to IwGame Usage. The new usage terms are shown below:

You are free to use IwGame in your projects in part or in whole as long as the header comments remain in-tact. Whilst you are not obliged to mention your usage of IwGame in your products it would be great and beneficial to let us know as we can publicise your product on our blog and other web sites / services (Our blog receives over 200,000 hits per month) However, if you use any part of the IwGame extensions system, which includes extension actors, extension scenes or extension modifiers then you are required to mention usage of the IwGame Engine in your product.

You may not claim the IwGame engine or its documentation as your own work or package it up and include it in any kind of middleware product without express prior written notice from an executive of Pocketeers Limited with the correct authority to grant authorisation. You may not publicly host any source code that is part of the IwGame Engine, the source will be hosted at http://www.drmop.com/index.php/iwgame-engine/

These changes apply to all versions of the IwGame Engine.

Well that’s it for this update